Conventionally, when performing, for example, drying, heating, and burning of a lime mud, foamable minerals, ceramics raw material powder, or the like, pyrolyzation of a rubber, a plastic waste, or the like, heat treatment or gasification treatment of a sewage sludge, a woody material, or the like, and carbonization of coal, a rotary kiln is widely employed as the heat treatment apparatus.
In a rotary kiln, there is an internal heating rotary kiln which heats directly treatment objects by injecting flame inside a cylindrical body (cylinder), which is supplied the treatment objects, by a burner, and an external heating rotary kiln which heats a cylindrical body from the outside thereof and heats indirectly treatment objects through the cylindrical body. In addition, one of the external heating rotary kiln has an outer cylinder around the inner cylinder (cylindrical body) rotating around an axis, the inner cylinder is heated from the outside thereof by which heating gas flows through the outer cylinder, and the inner cylinder is rotated and performs heat treatment while transferring the treatment objects inside the inner cylinder (for example, refer to Patent Document 1 and Patent Document 2).
In addition, for example, when low calorie materials (treatment objects) such as a sewage sludge, a woody biomass and low grade coal are reformed to carbide having a large calorific value similar to coal by the external heating rotary kiln (an external heating furnace or an external heating carbonization furnace), the inner cylinder is heated to a high temperature of 300 to 800° C., and performs heat treatment to the treatment objects at the condition of which oxygen is excluded. Thermal expansion and bending occurs to the inner cylinder when heated at a high temperature as above. Thus, conventionally, for example, in the inner cylinder, one end side along the axis, which is the inlet port side of the treatment objects, is rotatably supported around the axis by a movable support part, which is able to move along the axis, and the other end side along the axis, which is the outlet port side of the treatment objects, is rotatably supported around the axis by a fixed support part, which is unable to move along the axis, and the inner cylinder is provided so as to absorb the thermal expansion by the moving of the movable support part along the axis.